Cardiomyocyte hyperplasia and immaturity but not hypertrophy are characteristic features of patients with RASopathies.

AIMS: RASopathies are caused by mutations in genes that alter the MAP kinase pathway and are marked by several malformations with cardiovascular disorders as the predominant cause of mortality. Mechanistic insights in the underlying pathogenesis in affected cardiac tissue are rare. The aim of the study was to assess the impact of RASopathy causing mutations on the human heart. METHODS AND RESULTS: Using single cell approaches and histopathology we analyzed cardiac tissue from children with different RASopathy-associated mutations compared to age-matched dilated cardiomyopathy (DCM) and control hearts. The volume of cardiomyocytes was reduced in RASopathy conditions compared to controls and DCM patients, and the estimated number of cardiomyocytes per heart was ∼4-10 times higher. Single nuclei RNA sequencing of a 13-year-old RASopathy patient (carrying a PTPN11 c.1528C > G mutation) revealed that myocardial cell composition and transcriptional patterns were similar to <1 year old DCM hearts. Additionally, immaturity of cardiomyocytes is shown by an increased MYH6/MYH7 expression ratio and reduced expression of genes associated with fatty acid metabolism. In the patient with the PTPN11 mutation activation of the MAP kinase pathway was not evident in cardiomyocytes, whereas increased phosphorylation of PDK1 and its downstream kinase Akt was detected. CONCLUSION: In conclusion, an immature cardiomyocyte differentiation status appears to be preserved in juvenile RASopathy patients. The increased mass of the heart in such patients is due to an increase in cardiomyocyte number (hyperplasia) but not an enlargement of individual cardiomyocytes (hypertrophy).

TGF-ß activates pericytes via induction of the epithelial-to-mesenchymal transition protein SLUG in glioblastoma.

AIMS: In primary central nervous system tumours, epithelial-to-mesenchymal transition (EMT) gene expression is associated with increased malignancy. However, it has also been shown that EMT factors in gliomas are almost exclusively expressed by glioma vessel-associated pericytes (GA-Peris). In this study, we aimed to identify the mechanism of EMT in GA-Peris and its impact on angiogenic processes. METHODS: In glioma patients, vascular density and the expression of the pericytic markers platelet derived growth factor receptor (PDGFR)-ß and smooth muscle actin (αSMA) were examined in relation to the expression of the EMT transcription factor SLUG and were correlated with survival of patients with glioblastoma (GBM). Functional mechanisms of SLUG regulation and the effects on primary human brain vascular pericytes (HBVP) were studied in vitro by measuring proliferation, cell motility and growth characteristics. RESULTS: The number of PDGFR-ß- and αSMA-positive pericytes did not change with increased malignancy nor showed an association with the survival of GBM patients. However, SLUG-expressing pericytes displayed considerable morphological changes in GBM-associated vessels, and TGF-ß induced SLUG upregulation led to enhanced proliferation, motility and altered growth patterns in HBVP. Downregulation of SLUG or addition of a TGF-ß antagonising antibody abolished these effects. CONCLUSIONS: We provide evidence that in GA-Peris, elevated SLUG expression is mediated by TGF-ß, a cytokine secreted by most glioma cells, indicating that the latter actively modulate neovascularisation not only by modulating endothelial cells, but also by influencing pericytes. This process might be responsible for the formation of an unstructured tumour vasculature as well as for the breakdown of the blood-brain barrier in GBM.

Distribution and prognostic impact of microglia/macrophage subpopulations in gliomas.

While the central nervous system is considered an immunoprivileged site and brain tumors display immunosuppressive features, both innate and adaptive immune responses affect glioblastoma (GBM) growth and treatment resistance. However, the impact of the major immune cell population in gliomas, represented by glioma-associated microglia/macrophages (GAMs), on patients' clinical course is still unclear. Thus, we aimed at assessing the immunohistochemical expression of selected microglia and macrophage markers in 344 gliomas (including gliomas from WHO grade I-IV). Furthermore, we analyzed a cohort of 241 IDH1R132H-non-mutant GBM patients for association of GAM subtypes and patient overall survival. Phenotypical properties of GAMs, isolated from high-grade astrocytomas by CD11b-based magnetic cell sorting, were analyzed by immunocytochemistry, mRNA microarray, qRT-PCR and bioinformatic analyses. A higher amount of CD68-, CD163- and CD206-positive GAMs in the vital tumor core was associated with beneficial patient survival. The mRNA expression profile of GAMs displayed an upregulation of factors that are considered as pro-inflammatory M1 (eg, CCL2, CCL3L3, CCL4, PTGS2) and anti-inflammatory M2 polarization markers (eg, MRC1, LGMN, CD163, IL10, MSR1), the latter rather being associated with phagocytic functions in the GBM microenvironment. In summary, we present evidence that human GBMs contain mixed M1/M2-like polarized GAMs and that the levels of different GAM subpopulations in the tumor core are positively associated with overall survival of patients with IDH1R132H-non-mutant GBMs.

Differential expression of vascular endothelial growth factor A, its receptors VEGFR-1, -2, and -3 and co-receptors neuropilin-1 and -2 does not predict bevacizumab response in human astrocytomas.

BACKGROUND: A major hallmark of malignant progression in human astrocytomas is the formation of new blood vessels. Antiangiogenic therapy using the anti-vascular endothelial growth factor (VEGF)-antibody bevacizumab leads to increased progression-free survival in glioblastoma patients but does not influence their overall survival. To date, it is unclear why antiangiogenic therapy fails in many glioblastoma patients, while a small subpopulation profits considerably from this treatment. METHODS: The aim of our study was to determine the expression of VEGF-A and its (co-) receptors by immunohistochemistry and to test the association with patient survival in 350 glioma patients. Additionally, VEGF-A expression was analyzed by in-situ hybridization. In 18 patients, the protein expression was compared with the bevacizumab response according to extended and modified RANO criteria. RESULTS: We found a heterogeneous expression pattern of VEGF and its receptors in glioblastoma patients with significantly lower levels in WHO grade II and III tumors and normal-appearing brain tissue (P < .001). Pilocytic astrocytomas (WHO grade I) showed significantly higher VEGFR-1, -2 and neuropilin-1 levels as compared to WHO grade II and III astrocytomas (P < .01) but at lower levels than glioblastomas. The expression of neuropilin-2 was low in all tumors. There was neither a significant correlation between protein expression and patient survival nor between protein levels and bevacizumab response after modified RANO criteria. CONCLUSION: Since our data indicate that beneficial response to bevacizumab treatment is independent of the expression of VEGF-A and its (co-) receptors, further investigation is needed to decipher the underlying mechanisms of antiangiogenic treatment response.

ATP synthase deficiency due to TMEM70 mutation leads to ultrastructural mitochondrial degeneration and is amenable to treatment.

TMEM70 is involved in the biogenesis of mitochondrial ATP synthase and mutations in the TMEM70 gene impair oxidative phosphorylation. Herein, we report on pathology and treatment of ATP synthase deficiency in four siblings. A consanguineous family of Roma (Gipsy) ethnic origin gave birth to 6 children of which 4 were affected presenting with dysmorphic features, failure to thrive, cardiomyopathy, metabolic crises, and 3-methylglutaconic aciduria as clinical symptoms. Genetic testing revealed a homozygous mutation (c.317-2A>G) in the TMEM70 gene. While light microscopy was unremarkable, ultrastructural investigation of muscle tissue revealed accumulation of swollen degenerated mitochondria with lipid crystalloid inclusions, cristae aggregation, and exocytosis of mitochondrial material. Biochemical analysis of mitochondrial complexes showed an almost complete ATP synthase deficiency. Despite harbouring the same mutation, the clinical outcome in the four siblings was different. Two children died within 60 h after birth; the other two had recurrent life-threatening metabolic crises but were successfully managed with supplementation of anaplerotic amino acids, lipids, and symptomatic treatment during metabolic crisis. In summary, TMEM70 mutations can cause distinct ultrastructural mitochondrial degeneration and almost complete deficiency of ATP synthase but are still amenable to treatment.

Multifactorial modulation of susceptibility to l-lysine in an animal model of glutaric aciduria type I.

Glutaric aciduria type I is an inherited defect in L-lysine, L-hydroxylysine and L-tryptophan degradation caused by deficiency of glutaryl-CoA dehydrogenase (GCDH). The majority of untreated patients presents with accumulation of neurotoxic metabolites - glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA) - and striatal injury. Gcdh(-/-) mice display elevated levels of GA and 3-OH-GA but do not spontaneously develop striatal lesions. L-lysine-enriched diets (appr. 235 mg/d) were suggested to induce a neurological phenotype similar to affected patients. In our hands 93% of mice stressed according to the published protocol remained asymptomatic. To understand the underlying mechanism, we modified their genetic background (F1 C57BL6/Jx129/SvCrl) and increased the daily oral L-lysine supply (235-433 mg). We identified three modulating factors, (1) gender, (2) genetic background, and (3) amount of L-lysine. Male mice displayed higher vulnerability and inbreeding for more than two generations as well as elevating L-lysine supply increased the diet-induced mortality rate (up to 89%). Onset of first symptoms leads to strongly reduced intake of food and, thus, L-lysine suggesting a threshold for toxic metabolite production to induce neurological disease. GA and 3-OH-GA tissue concentrations did not correlate with dietary L-lysine supply but differed between symptomatic and asymptomatic mice. Cerebral activities of glyceraldehyde 3-phosphate dehydrogenase, 2-oxoglutarate dehydrogenase complex, and aconitase were decreased. Symptomatic mice did not develop striatal lesions or intracerebral hemorrhages. We found severe spongiosis in the hippocampus of Gcdh(-/-) mice which was independent of dietary L-lysine supply. In conclusion, the L-lysine-induced pathology in Gcdh(-/-) mice depends on genetic and dietary parameters.

MIF Receptor CD74 is Restricted to Microglia/Macrophages, Associated with a M1-Polarized Immune Milieu and Prolonged Patient Survival in Gliomas.

The macrophage migration inhibitory factor (MIF) receptor CD74 is overexpressed in various neoplasms, mainly in hematologic tumors, and currently investigated in clinical studies. CD74 is quickly internalized and recycles after antibody binding, therefore it constitutes an attractive target for antibody-based treatment strategies. CD74 has been further described as one of the most up-regulated molecules in human glioblastomas. To assess the potential relevance for anti-CD74 treatment, we determined the cellular source and clinicopathologic relevance of CD74 expression in human gliomas by immunohistochemistry, immunofluorescence, immunoblotting, cell sorting analysis and quantitative polymerase chain reaction (qPCR). Furthermore, we fractionated glioblastoma cells and glioma-associated microglia/macrophages (GAMs) from primary tumors and compared CD74 expression in cellular fractions with whole tumor lysates. Our results show that CD74 is restricted to GAMs in vivo, while being absent in tumor cells, the latter strongly expressing its ligand MIF. Most interestingly, a higher amount of CD74-positive GAMs was associated with beneficial patient survival constituting an independent prognostic parameter and with an anti-tumoral M1 polarization. In summary, CD74 expression in human gliomas is restricted to GAMs and positively associated with patient survival. In conclusion, CD74 represents a positive prognostic marker most probably because of its association with an M1-polarized immune milieu in high-grade gliomas.

Tumour necrosis factor receptor superfamily member 9 (TNFRSF9) is up-regulated in reactive astrocytes in human gliomas.

AIMS: The prognosis of patients with malignant gliomas is still dismal despite maximum treatment. Novel therapeutic alternatives targeting tumorigenic pathways are, therefore, demanded. In murine glioma models, targeting of tumour necrosis factor receptor superfamily (TNFRSF) 9 led to complete tumour eradication. Thus, TNFRSF9 might also constitute a promising target in human diffuse gliomas. As there is a lack of data, we aimed to define the expression pattern and cellular source of TNFRSF9 in human gliomas. METHODS: We investigated TNFRSF9 expression in normal human central nervous system (CNS) tissue and glioma specimens using immunohistochemistry, immunofluorescence and Western blotting techniques. RESULTS: Our results show that TNFRSF9 is considerably up-regulated in human gliomas when compared with normal brain tissue. In addition, our data provides evidence for an immune cell-independent de novo expression pattern of TNFRSF9 in mainly non-neoplastic reactive astrocytes and excludes classic immunological cell types, namely lymphocytes and microglia as the source of TNFRSF9. Moreover, TNFRSF9 is predominantly expressed in a perivascular and peritumoural distribution with significantly higher expression in IDH-1 mutant gliomas. CONCLUSIONS: Our findings provide a novel, TNFRSF9-positive, reactive astrocytic phenotype and challenge the therapeutic suitability of TNFRSF9 as a promising target for human gliomas.